Turbocharger compressor having adjustable trim mechanism including swirl inducers

Abstract

A centrifugal compressor for a turbocharger includes an inlet-adjustment mechanism operable to move between an open position and a closed position. The inlet-adjustment mechanism includes a plurality of blades disposed about the compressor air inlet and located within an annular space within the air inlet wall. The blades are pivotable about respective pivot points such that the blades extend radially inward from the annular space into the air inlet when the blades are in the closed position so as to form an orifice of reduced diameter relative to a nominal diameter of the inlet. Upstream surfaces of the blades include swirl inducers that are structured and arranged to impart either pre-swirl or counter-swirl to the air passing through the orifice into the compressor wheel.

What is claimed is: 
     
       1. A turbocharger, comprising:
 a turbine housing and a turbine wheel mounted in the turbine housing and connected to a rotatable shaft for rotation therewith, the turbine housing receiving exhaust gas and supplying the exhaust gas to the turbine wheel; 
 a centrifugal compressor assembly comprising a compressor housing and a compressor wheel mounted in the compressor housing and connected to the rotatable shaft for rotation therewith, the compressor wheel having blades and defining an inducer portion, the compressor housing having an air inlet wall defining an air inlet for leading air generally axially into the compressor wheel, the compressor housing further defining a volute for receiving compressed air discharged generally radially outwardly from the compressor wheel, the air inlet wall defining an annular space surrounding the air inlet and open to the air inlet at a radially inner end of the annular space; and 
 a compressor inlet-adjustment mechanism disposed in the annular space of the air inlet wall and movable between an open position and a closed position, the inlet-adjustment mechanism comprising a plurality of blades disposed within the annular space, the blades collectively circumscribing an orifice, each blade having an upstream surface relatively farther from and facing away from the compressor wheel and a downstream surface relatively closer to and facing toward the compressor wheel, the blades pivoting about respective pivots radially inwardly from the annular space into the air inlet when the blades are in the closed position so as to cause the orifice to have a reduced diameter relative to a nominal diameter of the inlet; 
 wherein the upstream surface of each of the blades includes a plurality of circumferentially spaced swirl inducers that are structured and arranged to impart swirl to the air passing through the orifice into the compressor wheel. 
 
     
     
       2. The turbocharger of  claim 1 , wherein the swirl inducers comprise slots in the upstream surface of each blade. 
     
     
       3. The turbocharger of  claim 2 , wherein the slots are oriented to impart pre-swirl to the air. 
     
     
       4. The turbocharger of  claim 2 , wherein the slots are oriented to impart counter-swirl to the air. 
     
     
       5. The turbocharger of  claim 1 , wherein the radially inner edge of each blade has a circular-arc shape, the blades being configured so that said radially inner edges collectively form the orifice as substantially circular in a selected position of the inlet-adjustment mechanism. 
     
     
       6. The turbocharger of  claim 1 , wherein the number of said blades is three. 
     
     
       7. The turbocharger of  claim 1 , wherein the inlet-adjustment mechanism further comprises a unison ring, the unison ring being rotatable about a rotational axis of the turbocharger, wherein each of the blades is engaged with the unison ring such that rotation of the unison ring causes the blades to pivot. 
     
     
       8. The turbocharger of  claim 7 , wherein each blade includes an end portion that engages an outer periphery of the unison ring.